Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During operation of a wind turbine, various components of the wind turbine are subjected to various loads due to the aerodynamic wind loads acting on the blade. The blade loading is dependent on the wind speed, tip speed ratio and/or pitch setting of the blade. Tip speed ratio is the ratio of the rotational velocity of the blade tip to wind speed. It can be desirable to adjust operation of the wind turbine based on signals indicative of tip speed ratio (e.g. various speed readings) to adjust loading of the rotor blades of the wind turbine and/or to increase energy production of the wind turbine.
To reduce rotor blade loading, various methods and apparatus have been developed to allow the rotor blades to shed a portion of the loads experienced thereby. Such methods and apparatus include, for example, pitching the rotor blades and/or reducing generator torque during operation. Accordingly, many wind turbines include a wind turbine controller that can operate the wind turbine in various ways based on the tip speed ratio wind turbine loading. For instance, under various operating conditions, the wind turbine can adjust the torque of a generator and/or the pitch angle of the rotor blades to adjust the tip speed ratio to meet a desired tip speed ratio setpoint to increase energy capture by the wind turbine.
The pitch angle of a rotor blade can be controlled, for instance, using a wind pitch adjustment system. The wind pitch adjustment system can include a motor, such as a direct current (DC) motor driven by a DC/DC converter. In some implementations, a wind pitch adjustment system includes a DC source, a control circuit, an inverter bridge, and/or a DC bus capacitor bank having one or more capacitor devices.
The wind turbine and/or the pitch adjustment system can receive power from an electrical grid. In some instances, voltage surges caused by various grid events, such as a high voltage ride-through grid event can damage various components of the wind turbine system and/or the pitch adjustment system if preventative action is not taken. Some pitch adjustment systems can include a dynamic braking device configured to suppress voltage surges associated with a grid event.